Glass reinforced plastics recoilless rifle



Jan. 17, 1967 F. R. BARNET ETAL GLASS REINFORCED PLASTICS RECOILLESS RIFLE Filed Jan; 8, 1965 Fredrick R. Barnet Stanley R Prosen INVENTORS.

BY ATTORNEY.

AGENT.

United States Patent 3,298,279 GLASS REINFORCED PLASTICS RECGILLESS RIFLE Fredrick R. Barnet, Kensington, and Stanley P. Prosen,

Lanham, Md., assignors to the United States of America as represented by the Secretary of the Navy Filed Jan. 8, 1965, Ser. No. 425,117

10 Claims. (Cl. 89-1814) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to a recoilless rifle for firing a rocket-assist projectile, and more particularly to an expendable recoilless rifle which may be inexpensively manufactured and discarded after firing one shot.

In the past, recoilless rifles have been manufactured from steel or aluminum but these materials become strategic in war time due to the demand for their extensive use in the war time armament program. The use of steel or aluminum for the construction of expendable guns carried on pursuit aircraft is not feasible because these materials may be recovered by the enemy when the guns are jettisoned and subsequently used in the manufacture of weapons by the enemy. Moreover, the manufacture of recoilless rifles from steel and aluminum produces a heavy weapon which adversely impairs the speed and maneuverability of a pursuit aircraft upon which these weapons are to be mounted.

The present invention provides an inexpensive expendable recoiless rifle adapted to be carried by a pursuit aircraft and jettisoned by the aircraft after firing of the weapon. The recoilless rifle of the present invention is manufactured from materials which are light weight, inexpensive, strong, and which do not become scarce or strategic in the time of war.

An object of the present invention is to provide an expendable recoilless rifle for firing a rocket-assist projectile.

Another object is to provide an inexpensive recoilless rifle for firing a rocket-assist projectile reliably throughout a wide range of temperatures and altitudes experienced by a pursuit type aircraft.

A further object of the invention is the provision of a recoilless rifle designed for firing a rocket-assist projectile from any altitude and which is highly resistant to the elements of weather.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following description of a preferred embodimentof the invention as illustrated in the accompanying sheetof drawings in which:

FIGURE 1 shows a plan view, partly in section, of a preferred embodiment of the invention;

FIGURE 2 illustrates a section of the device taken along line 22 of FIGURE 1; and

FIGURE 3 illustrates a section of the device taken along line 33 of FIGURE 1.

Referring to FIGURE 1 of the drawings there is shown a recoilless rifle 10 designed to be carried by a pursuit type aircraft and to fire one 2.75 inch rocket-assist projectile and then to be jettisoned from the aircraft. Due to the fact that the gun is to be carried under the wings of a pursuit type aircraft, it is desirable that the gun be constructed of light weight material having high strength properties so that a small gun may be developed to minimize the aerodynamic drag upon the aircraft and to minimize the amount weight added to the aircraft by the attachment of a plurality of these guns. For this reason, the gun of the present invention has been constructed entirely of a strong light weight plastic material,

- tile.

3,298,279 Patented Jan. 17, 1967 with the exception of the metallic firing pins. The gun illustrated in FIGURE 1 is adapted to be carried under the wings of a pursuit aircraft in clusters of three or more, each cluster being attached to the aircraft by means of the aircrafts conventional bomb release mechanisms. Each recoilless gun 10 is comprised of a smooth bore section 11 into which the rocket-assist projectile is loaded prior to firing and a rifled barrel section 12 having lands and grooves formed on the inner peripheral surface thereof to engage the rotating band of the rocketassist projectile to impart suflicient rotational spin to the projectile to enhance the stability of flight of the projec- According to the preferred embodiment of the present invention, the recoilless rifle-d gun barrel is constructed of a glass fiber strand reinforced plastic and is fabricated upon a specially designed mandrel. The mandrel may consist of a cylindrical shaft having a diameter equal to the inner diameter of the gun barrel to be produced, and having a smooth outer surface on one portion thereof for forming the smooth bore section 11 of the gun barrel and having spiral grooves formed in the remainder of the mandrel surface to form the lands 13 on the interior of the rifled barrel section 12. When winding the gun barrel upon the mandrel, conventional glass rovings such as 8 end 150-1/0-114 may be wound upon the mandrel and a plastic binder applied to the roving immediately thereafter or during the winding operation. At the beginning of the winding operation, a plurality of continuous glass fiber strands or filaments 15 are laid in the spiral grooves formed in the outer peripheral surface of a portion of the mandrel and any thermosetting resin binder of suitable viscosity and workability is applied to the strands along with either an amine type curing agent or an anhydride type curing agent or any other suitable curing agent. By way of an example, an epoxy resin available from Shell Chemical Company by the name of Epon 828 (epoxy equivalent 180l95) may be used with the curing agent tris(dimethylarninomethyl) phenol tri(2- ethyl hexoate) also available from Shell Chemical Company as curing agent D. The remainder of the gun barrel thickness was fabricated by forming oppositely wound helical windings of continuous glass fiber roving or yarn having the resin and curing agent impregnated therein or applied during the winding operation. The fabricated barrel must then be cured for a suitable time and temperature dependent upon the particular binder and curing agent used. It was found that satisfactory curing was achieved by heating the barrel at 250 F. for 2 /2 hours when the aforementioned Epon 828 and curing agent D were used. After the curing was completed, the mandrel was removed.

According to the preferred embodiment the present invention, the thickness of the gun barrel exclusive of the lands 13 was 0.25 inch, the walls of the barrel being fabricated by using two angles of wind, the inner .0085

inch of thickness being wound with roving at an angle of 65 /2 to the axis of the mandrel and the outer 0.165 inch of thickness being wound at an angle of 79 /3 to the axis of the mandrel. The mandrel was designed with an outer diameter of 2.820 inches for the fabrication of a gun barrel having a similar inner diameter to accommodate 2.75 inch rocket-assist projectiles. The particular angles selected for the winding of the glass roving were calculated to provide a hoop-to-axial strength ratio of 30:1 which was considered to be adequate to handle the maximum anticipated stresses encountered by the Weapon.

The breech end of the gun barrel is provided with screw threads 16 formed in the inner peripheral wall of said barrel to receive a thrust nozzle 17 which is provided with external screw threads 18 for threaded coupling engagement with the internal threads 16 of the gun barrel. The

J nozzle 17 is compression molded from a glass-filled high temperature phenolic 9lLD type CTLMS, manufactured by the American Reinforced Plastics Company, Los Angeles, California. This material was selected for the nozzle because of its high resistance to exhaust gas erosion.

To provide means for firing a rocket-assist projectile, a pair of electrically conductive pins 19 and 20 are mounted in the wall of the smooth bore section ll of the barrel and extend externally of said barrel wall for insertion into female electrical contacts when the weapon is mounted beneath the wings of an aircraft. Each electrically conductive pin has formed on one end thereof an arcuate conductive strip 21 having a radius of curvature substantially equal to the radius of curvature of the interior of the gun barrel. The electrically conductive pins and their arcuate strips may be mounted within the gun barrel after the barrel has been fabricated, or they may be placed upon the mandrel and the glass roving wound about the pins in such a manner that the pins are mounted within the wall of the gun barrel when the mandrel is withdrawn from the fabricated barrel.

To permit easy loading of the rocket-assist projectile, the exhaust nozzle 17 is detachably connected to the gun barrel by means of screw threads 16 and 18 so that the nozzle may be uncoupled from the gun barrel and the projectile inserted within the smooth bore section of the gun and the nozzle again threadedly coupled to the gun barrel. The projectile is provided with a rotating band to impart rotational spin to the projectile as the projectile passes through the rifled section 12 of the barrel. The particular rotating bands utilized the projectile fired by this weapon are to receive the lands of the rifled barrel section 12. The weapon is designed with the smooth bore section 11 of such a length that when the rocket-assist projectile is loaded within the smooth bore section, the forward shoulder 22 of the nozzle 17 abuts against the rear wall of the projectile to hold the projectile securely within the smooth bore section 11 and, in this position, the pre-engraved rotating band on the projectile engage the lands 13 at the beginning of the rifled barrel section 12. As the projectile is held in this position by the forward shoulder 22 of the nozzle 17, the electrically conductive arcuate strips 21 are in contact with annular electrically responsive segments of the projectile so that, when a suitable electrical impulse is applied to the electrically conductive firing pins 19 and 20, the rocket-assist projectile is ignited and fired down the rifled barrel section of the weapon.

From the foregoing, it is seen that the present invention provides rifled gun for launching a rocket-assist projectile from beneath the wings of an aircraft. The gun is constructed of a light weight material which is very strong and inexpensive to manufacture, thus adding little additional weight to the aircraft and being suitable for jettisoning after the projectile has been fired. In view of the fact that the gun is constructed of a glass fiber reinforced plastic, the gun is light, very strong, and may be readily jettisoned without surrendering strategic materials to the enemy.

When fabricating the recoilless rifled gun barrel, it is possible to use various other mandrels than the previously described one piece steel mandrel which is unthreaded from the gun barrel after the barrel has been fabricated and cured. It is possible to utilize a mandrel which is of the collapsible type or alternatively to mold a mandrel of a chipable plaster material, which may be readily broken apart after the gun barrel has been wound and cured. Moreover, it is also possible to construct a mandrel from a granular material molded together and held in the predetermined configuration by means of a soluble adhesive or binder, and then dissolving the adhesive or granular material after the gun barrel has been fabricated to dissolve the mandrel. It is also within the scope of the present invention to fabricate a gun barrel similar to the one shown in FIGURE 1 by molding the barrel from a glass reinforced plastic material and then cutting the rifling into the inner peripheral surface of the barrel. It is further possible to first mold the gun barrel from the glass reinforced plastic material or other suitable ma terials and then cover the molded tubular gun barrel by glass roving or glass fabric. The method employed within the manufacture of the gun barrel of the rifled recoilless gun may be utilized in the manufacture of numerous other types of gun barrels or weapons.

Obviously many other modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A recoilless rocket launcher comprising 7 an elongated cylindrical gun barrel having a smooth bore section and a rifled barrel section,

said smooth bore section being constructed of glass reinforced plastic material and having a pair of metallic electrically conductive pins mounted therein and extending through the wall of said smooth bore section,

a pair of arcuate electrically conductive strips in contact With said pins and positioned within said smooth bore section and extending a substantial distance over a circumference of said smooth bore section, the portion of said conductive strips in contact with said smooth bore section having a radiusof curvature substantially equal to the radius of curvature of said smooth bore section,

an annular nozzle having an inwardly converging and diverging surface mounted on the inner peripheral surface of one end of said smooth bore section, said nozzle having screw threads formed on the outer peripheral surface for engagement with screw threads formed in the inner peripheral surface of said one end of said barrel, 1

whereby a rocket-assist projectile may be inserted within the smooth bore section of said rocket launcher and the nozzle subsequently threaded into said one end of the barrel to load the rocket launcher.

2. The rocket launcher of claim 1 wherein'said rifled barrel section of said rocket launcher is defined by a plurality of spiral lands formed on the inner peripheral surface of said cylindrical barrel.

3. The rocket launcher of claim 2 wherein each of said lands comprises a plurality of continuous glass fiber strands disposed parallel to one another in a spiral configuration along the inner peripheral surface of said barrel and being bonded together by a suitable glass fiber binder.

4. The rocket launcher of claim 3 wherein said glass 4 reinforced plastic gun barrel comprises a plastic mass having bonded therein a helically wound continuous strand of glass roving.

5. The rocket launcher of claim 4 wherein said glass roving is oppositely wound in a plurality of layers.

6. The rocket launcher of claim 3 wherein, said glass reinforced plastic gun barrel comprises a mass of plastic material having entrained therein a continuous glass strand being helically formed in a plurality of layers, some of said layers being wound in a greater angle to the axis of said barrel than the other of said layers to impart a predetermined hoop-to-axial strength ratio to said barrel. 7. A method of manufacturing a glass reinforced plastic gun barrel comprising applying a film of lubricant upon the outer surface of a cylindrical mandrel having a smooth outer surface along a portion of its length and the remainder of the outer surface of said mandrel being provided with a continuous spiral groove cut into the surface of said mandrel, winding a plurality of continuous glass fiber roving longitudinally within said spiral groove,

applying a binder material and a curing agent to said roving in said spiral grooves,

simultaneously winding continuous glass fiber roving upon the said mandrel in a helical pattern while applying a binder material and a curing agent to the roving as it is wound upon the mandrel,

and curing said helically wound gun barrel at an elevated temperature for a predetermined duration of time.

8. The method of claim 7 further comprising simultaneously winding additional layers of continuous glass roving upon said mandrel in a helical pattern While applying a binder and a curing agent to the glass roving,

said additional layers being wound at a diflferent angle to the axis of said mandrel than the previously mentioned layers,

whereby the gun barrel produced by this method may be provided with a predetermined hoop-to-axial strength ratio.

9. T he .method of manufacturing a glass reinforced plastic gun barrel comprising applying a film of lubricant upon a cylindrical mandrel having a smooth outer surface along a portion of the length thereof and having a continuous spiral groove cut along the outer peripheral surface of the remaining length of said mandrel,

mounting electrically conductive firing pins upon said mandrel,

winding a plurality of parallel continuous glass fiber strands within said spiral groove,

applying a binder and curing agent to said continuous glass fiber strands in said spiral groove,

winding a plurality of layers of continuous glass fiber strands upon said mandrel in a helical pattern at an angle to the axis of said mandrel,

applying a suitable binder and curing agent to said glass fiber strands as they are wound upon the mandrel,

continuing the winding operation until the thickness of the barrel approaches the length of the metallic firing pins, and

curing the gun barrel at a suitable temperature and time duration.

10. The method of claim 9 wherein certain of the plurality of layers of continuous glass fiber strands are wound at a greater angle to the axis of said mandrel than other of said layers to provide the gun barrel with a predetermined hoop-to-axial strength ratio.

References Cited by the Examiner UNITED STATES PATENTS 2,629,894 3/1953 Boggs 156-175 X 2,701,985 2/1955 Smith 89-1.7 2,847,786 8/1958 Hartley et a1. 42-76 3,129,636 4/1964 Strickland et a1. 89l.7

FOREIGN PATENTS 578,034 6/1959 Canada. 89,970 8/ 1937 Sweden.

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL W. ENGLE, Examiner. 

1. A RECOILLESS ROCKET LAUNCHER COMPRISING AN ELONGATED CYLINDRICAL GUN BARREL HAVING A SMOOTH BORE SECTION AND A RIFLED BARREL SECTION, SAID SMOOTH BORE SECTION BEING CONSTRUCTED OF GLASS REINFORCED PLASTIC MATERIAL AND HAVING A PAIR OF METALLIC ELECTRICALLY CONDUCTIVE PINS MOUNTED THEREIN AND EXTENDING THROUGH THE WALL OF SAID SMOOTH BORE SECTION, A PAIR OF ARCUTE ELECTRICALLY CONDUCTIVE STRIPS IN CONTACT WITH SAID PINS AND POSITIONED WITHIN SAID SMOOTH BORE SECTION AND EXTENDING A SUBSTANTIAL DISTANCE OVER A CIRCUMFERENCE OF SAID SMOOTH BORE SECTION, THE PORTION OF SAID CONDUCTIVE STRIPS IN CONTACT WITH SAID SMOOTH BORE SECTION HAVING A RADIUS OF CURVATURE SUBSTANTIALLY EQUAL TO THE RADIUS OF CURVATURE OF SAID SMOOTH BORE SECTION, AN ANNULAR NOZZLE HAVING AN INWARDLY CONVERING AND DIVERGING SURFACE MOUNTED ON THE INNER PERIPHERAL SURFACE OF ONE END OF SAID SMOOTH BORE SECTION, SAID NOZZLE HAVING SCREW THREADS FORMED ON THE OUTER PERIPHERAL SURFACE FOR ENGAGEMENT WITH SCREW THREADS FORMED IN THE INNER PERIPHERAL SURFACE OF SAID ONE END OF SAID BARREL, WHEREBY A ROCKET-ASSIST PROJECTILE MAY BE INSERTED WITHIN THE SMOOTH BORE SECTION OF SAID ROCKET LAUNCHER AND THE NOZZLE SUBSEQUENTLY THREADED INTO SAID ONE END OF THE BARREL TO LOAD THE ROCKET LAUNCHER. 